JP2956149B2 - Projection display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display device that displays video images, computer images, and the like. In particular, the present invention relates to a display device that projects a liquid crystal light valve or the like obliquely from the back.

[Conventional technology]

2. Description of the Related Art In recent years, a display device using a transmissive or reflective dot matrix liquid crystal (hereinafter, referred to as a light valve) has been used. Attention has been paid.

This is naturally limited in the size of image display using a cathode ray tube (CRT). Larger screens are accompanied by the larger size of the cathode ray tube itself, and practically the size is limited to about 40 inches. This is in order to meet the demand for obtaining an image.

On the other hand, in order to increase the area of the light valve itself, it is not easy to obtain a large-sized liquid crystal display device having no defects in manufacturing, and even if obtained, it becomes extremely expensive.

For this reason, if a transmissive (or reflective) light valve is used to magnify and project an image displayed thereon, a powerful large screen can be obtained without being limited by the size of the screen. It is possible.

Therefore, a display type display device in which an optical system for magnifying and projecting using a light valve is housed in a cabinet, and a rear surface is projected on a screen provided on the front of the cabinet so that an enlarged image can be viewed from the front of the cabinet. Has been provided.

A conventional rear-projection display device using a light valve of this type provides illumination from a light source to a transmissive liquid crystal panel, as shown in, for example, Japanese Utility Model Application Laid-Open No. 1-85778, and the liquid crystal panel displays the light. In this structure, an image is enlarged by a projection lens, the optical path is changed by a reflection mirror, and the image is guided to the back of the screen. In this way, the entire projection optical system is housed in the cabinet, can be moved to an arbitrary place, and the image on the screen can be viewed even in a bright room.

However, in the conventional display type rear projection display device, since the light flux transmitted through the light valve is converted into an optical path by a reflection mirror and guided to the rear of the screen, the light must be projected with an optical axis perpendicular to the screen. Since the image is distorted due to trapezoidal distortion or the like, the installation conditions of the reflection mirror are greatly restricted, and as a result, the volume occupied by the projection optical system, particularly the depth dimension (the cabinet thickness) with respect to the screen, increases. Therefore, a rear projection display device using a thin cabinet cannot be provided.

Therefore, an oblique projection method can be considered as a means for solving this. Generally, the image of a lens with a tilted object is a US patent
As shown by T. Scheimpflug in No. 751,347, trapezoidal distortion occurs. In FIG. 12, the inclined object surface 13 forms an image on the inclined image surface 15 by the lens 14. As shown in FIG. 12, the relationship between the tilts is such that the extension of the object plane 13, the lens 14, and the image plane 15 coincide with each other. Assuming that the point of intersection between the perpendicular to the optical axis Z of the image-side focal point F of the lens 14 and the image plane 15 is g, the image on the square object surface shown in FIG. 13 is formed into a trapezoidal shape shown in FIG. An image is formed on the image plane 15.

Therefore, in order to remove the trapezoidal distortion, the light valve 16, the first projection lens 17, the second projection lens 19, and the screen 20 are arranged at an angle to the optical axis Z as shown in FIG. Here, the intersection g ₁ between the first image plane 18 of the image-side focal point F ₁ with the first projection lens 17 and a plane parallel to the trapezoidal distortion as the projection lens 17, those of the second projection lens 19 The intersection point g ₂ ′ between the plane passing through the side focal point F ₂ ′ and parallel to the second projection lens 19 and the image plane 18 having trapezoidal distortion is matched.

At this time, for example, the image of the square light valve shown in FIG. 16 becomes an image with trapezoidal distortion shown in FIG.
An image without trapezoidal distortion shown in FIG. 18 is formed above. Therefore,
If this projection optical system is bent by the first mirror 9 and the second mirror 10 as shown in FIG. 2 and housed in the cabinet 7, a thin rear projection display device can be constructed.

[Problems to be solved by the invention]

However, while the above-described projection optical system can eliminate trapezoidal distortion, there is a problem in that a difference in magnification between the vertical direction and the horizontal direction, that is, image stretching occurs.

Therefore, the present invention solves such a problem,
It is an object of the present invention to provide a display device of oblique projection without stretching between images.

[Means for solving the problem]

The present invention includes a light modulation unit that modulates light from a light source, and a projection unit that projects an image of the light modulation unit on a projection surface, and an optical axis of the projection unit does not perpendicularly intersect the projection surface. In a projection display apparatus, the projection unit includes a first projection optical unit that forms an image having a trapezoidal distortion from an image formed by the light modulation unit, and a trapezoid formed by the first projection unit. A second projection optical unit for forming an image having no trapezoidal distortion from a distorted image, and a third projection optical unit for correcting an elongation of an image formed by the second projection unit; The projection optical unit of No. 3 is an anamorphic optical system.

[Action]

According to the above configuration of the present invention, the image of the transmission type or reflection type light modulating means is formed as an image having trapezoidal distortion by the first projection optical means, and the image having trapezoidal distortion is formed in the second projection optical means. The third projection optical system, which is formed as an image without trapezoidal distortion by the optical means and is an anamorphic optical system including at least one set of toric lens or cylindrical lens, corrects the elongation during the projected image on the screen. You.

〔Example〕

Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of an oblique projection optical system arrangement according to the present invention.
The figure shows an example of an image of a light valve, FIG. 4 shows an intermediate image having trapezoidal distortion, and FIG. 5 shows an image on a screen without trapezoidal distortion. In FIG. 1, a light valve 1, a first projection lens 2, a second projection lens 4, and a screen 6 are shown.
Are inclined by φ ₁ , φ ₂ , φ ₃ , φ _{4 with} respect to the optical axis Z, respectively. The third projection optical system 5 is arranged near the second projection lens 4 along the optical axis or inclined. The image of the transmission or reflection type light valve 1 is formed into an intermediate image 3 having trapezoidal distortion by the first projection lens 2 inclined with respect to the light valve. The inclination of the intermediate image 3 is obtained in the same manner as in FIG. At this time, the square image on the light valve 1 shown in FIG. 3 is formed by the first projection lens 2 into a trapezoid shown in FIG. The inclination of the second projection lens 4 and the screen 6 with respect to the intermediate image 3 having the trapezoidal distortion is determined in the same manner as in FIG. 15, and the first projection lens 2 passes through the image-side focal point F1 of the _first projection lens 2. Intermediate image 3 with plane parallel to lens 2 and trapezoidal distortion
The intersection g ₁ and, to match the second projection lens 4 of the object-side focal point F 'intersection g ₂ between the intermediate image 3 with a through a second projection lens 4 and the plane parallel to the trapezoidal distortion' ₂ . At this time, the intermediate image 3 having trapezoidal distortion is formed as an image without trapezoidal distortion on the screen 6 by the second projection lens 4, and the third projection optical system 5 sets a difference in magnification between the x direction and the y direction, that is, The stretch between the images is corrected, and an image without trapezoidal distortion or stretch is formed on the screen 6 as shown in FIG.

The first projection lens 2 and the second projection lens 4 are
As shown in the figure, it is also possible to configure by a combination lens which is inclined to correct the aberration. As the screen 6, a rear screen used for a rear projection television or the like can be used. This is to improve the light distribution characteristics by combining a lenticular lens and a Fresnel lens sheet with a resin substrate containing a diffusing agent. However, when the light is projected obliquely as in the present invention, the total reflection of the prism is used so that a part of the light projected on the screen 6 is enlarged in FIG. It is desirable to use a screen whose light distribution characteristics are good for oblique projection by combining a sheet that directs the incident light beam in a direction substantially perpendicular to the front surface of the screen 12 with a sheet of a lenticular lens.

6 and 7 show a first embodiment 1 of the third projection optical system 5, wherein FIG. 6 is a yz sectional view and FIG. 7 is an xz sectional view.
By arranging the two toric lenses so as to be substantially confocal on the yz plane and the xz plane, an anamorphic optical system having different magnifications in the y direction and the x direction can be realized. If the ratio of the magnification of the third projection optical system 5 in the y direction and the x direction is the reciprocal of the ratio of the magnification of the image by the first projection lens 2 and the second projection lens 4 in the y direction and the x direction, The third projection optical system 5 can correct the extension of the image on the screen 6.

8 and 9 show a second embodiment of the third projection optical system 5. FIG. The two cylindrical lenses are arranged so as to be almost confocal. As in the present embodiment, one of the lenses has a positive refractive power and the other has a negative refractive power, whereby the distance between the lenses can be reduced.

〔The invention's effect〕

As described above, according to the present invention, there is no trapezoidal distortion, but by adding projection optical means for compensating for the elongation to the oblique projection type display device having the elongation between the images, the elongation between the images on the screen is improved. Has the effect of correcting In addition, since images are not distorted even when projected obliquely, the volume, particularly the depth, of the cabinet can be significantly reduced when incorporated into a cabinet to form a rear projection display device, and a compact display device is provided. can do.

[Brief description of the drawings]

FIG. 1 is an arrangement diagram of an oblique projection optical system according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Light valve 2 ... First projection lens 3 ... Intermediate image with trapezoidal distortion 4 ... Second projection lens 5 ... Third projection optical system 6 ... Screen FIG. FIG. 2 is a cross-sectional view of a configuration example of a rear projection display device using an oblique projection optical system. 7 Cabinet 8 Projection optical unit 9 First mirror 10 Second mirror 11 Screen FIGS. 3, 4 and 5 show the light valves of FIG. 1 according to the present invention, respectively. Explanatory drawing of an intermediate image and the image formation on a screen. 6 and 7 are sectional views of a first embodiment of the third projection optical system according to the present invention. 8 and 9 are cross-sectional views of a second embodiment of the third projection optical system according to the present invention. FIG. 10 is a sectional view of an embodiment of a first projection lens and a second projection lens used in the present invention. FIG. 11 is a partially enlarged view of a cross section of a screen due to total reflection of a prism used in the present invention. 12 Screen FIG. 12 is an explanatory diagram of image formation on an inclined object surface. 13: inclined object surface 14: lens 15: inclined image surface FIGS. 13 and 14 are explanatory views of the imaging of the object surface and the image surface in FIG. FIG. 15 is a sectional view of an oblique projection optical system. 16 Light valve 17 First projection lens 18 Image plane with trapezoidal distortion 19 Second projection lens 20 Screen FIG. 16, FIG. 17, and FIG. Light bulb,
FIG. 3 is an explanatory diagram of an image plane having trapezoidal distortion and image formation on a screen.

Claims (2)

(57) [Claims] A light modulating means for modulating light from a light source; and a projecting means for projecting an image of the light modulating means on a projecting surface, wherein an optical axis of the projecting means and the projecting surface intersect perpendicularly. A projection display device, wherein the projection unit is formed by a first projection optical unit that forms an image with a trapezoidal distortion from an image formed by the light modulation unit, and the first projection unit. A second projection optical unit for forming an image having no trapezoidal distortion from an image having a trapezoidal distortion, and a third projection optical unit for correcting an elongation of an image formed by the second projection unit, The projection type display device, wherein the third projection optical means is an anamorphic optical system. 2. The projection type display device according to claim 1, wherein
The projection display device, wherein the anamorphic optical system includes at least one set of a toric lens or a cylindrical lens.